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+// RUN: %dafny /compile:0 "%s" > "%t"
+// RUN: %diff "%s.expect" "%t"
+
+class Cell {
+ var data: int
+
+ predicate P()
+ reads this
+ { data < 0 }
+
+ predicate Q(e: Cell)
+ reads this, e
+ { e != null ==> e.data == data }
+
+ method Test() {
+ ghost var b;
+ var c := new Cell;
+ if {
+ // In the current state, everything is allowed:
+ case true => b := this.P();
+ case true => b := c.P();
+ case true => b := this.Q(this);
+ case true => b := this.Q(c);
+ case true => b := c.Q(this);
+ case true => b := c.Q(c);
+
+ // 'this' was allocated already in the 'old' state, so all of these are fine:
+ case true => b := old(this.P());
+ case true => b := old(P()); // same as previous line, of course
+ case true => b := old(this.Q(this));
+
+ // 'c' is freshly allocaed in this method, so it cannot be used inside 'old'
+ case true => b := old(c.P()); // error: receiver argument must be allocated in the state in which the function is invoked
+ case true => b := old(c.Q(this)); // error: receiver argument must be allocated in the state in which the function is invoked
+
+ // The same rule should apply if 'c' is a non-receiver argument
+ case true => b := old(this.Q(c)); // BOGUS: this should also generate an error
+
+ // In the following, 'c' is used as both of the two arguments. It's not allowed as either argument. However, since the error
+ // about the receiver masks the error about the other parameter, only one error (about the receiver) should be reported.
+ case true => b := old(c.Q(c)); // BOGUS: this should generate an error about the receiver
+ }
+ }
+}
+